1. Field of the Invention
The present invention relates generally to systems for steering motorboats and, more particularly, to a steering system for a high performance powerboat which utilizes a secondary, fin-like rudder located forward to the main, aft rudder for providing improved steering and stabilizing capabilities to the boat, especially during sharp, high speed turns or when the boat is towing a water-skier.
2. Description of Related Art
Powerboats are available in numerous shapes and sizes and can have varying hull constructions along with different propulsion systems. There are two basic types of hull designs for powerboats, namely displacement and planing hulls, with many variations of the planing hulls. Displacement boats are characterized as vessels that cruise through water while planing boats are designed to lift a part of the hull out of the water to skim the surface of the water. Planing boats have become increasingly popular and are used in activities which require high speed performance, such waterskiing and powerboat racing.
There are also different types of propulsion systems to choose from which differ in the manner in which the engine is placed on the boat and the power that can be generated. For example, an inboard system, in which the engine is mounted within the hull of the boat, and an outboard system, in which the engine is mounted on a transom of the boat and is detachable, are two widely used propulsion systems for powerboats. Another type of system, called a stern-drive system and sometimes referred to as an inboard-outboard, I-O, or outdrive system, utilizes an engine mounted inside the hull of the boat with a portion of the drive unit, resembling the lower portion of an outboard motor, extending through the transom. All of these types of systems utilize the same basic concept of creating thrust or propulsion through rotation of a propeller which draws water ahead and pushes it astern to propel the boat through water.
Although outboard, stern-drive and inboard systems rely on propeller propulsion to move the boat through the water, the steering systems associated with each propulsion system differs significantly in handling and construction. On an single-screw, inboard powerboat, the shaft and propeller are fixed along the centerline of the hull since the engine is mounted within the hull of the boat. Steering on an inboard powerboat is accomplished through the use of a vertical rudder blade pivoted on a stock and located near the stern of the boat in close proximity to the propeller. Outboard and stern-drive boats, on the other hand, use directed-thrust steering, usually without the help of a rudder, to propel and steer the boat through water.
Powerboats used to tow water-skiers encounter unique handling problems since large forces can be generated by the dynamic action of the water-skier and directly transmitted to the stern of the boat via the towline. The action of the water-skier can generate a large force that can act on the stern of the boat causing it to slip or "kickout" in the general direction of the force causing the boat to deviate from its original direction. When this occurs, the operator of the boat must compensate for the pulling force by quickly turning the steering wheel to straighten the boat out in order to maintain the desired course of travel.
The pull on the stern of the boat is particularly critical when the boat itself is making a turn since the stern of the boat has a natural tendency to kickout somewhat to the side opposite the direction of the turn. Depending upon the position and pull generated by the skier via the towline, the stern of the boat can be pulled out further by the water-skier causing the boat to deviate sharply from its intended line of travel. Again, when this occurs, the operator of the boat must compensate by quickly turning the steering wheel to attempt to straighten out the boat to the desired line of travel.
Competition powerboats are particularly susceptible to the dynamic effects of a towed skier in competition water events such as the slalom. In this particular event, the powerboat pulls the skier through a series of pylons which are set to the left and right of the powerboat which the skier must successfully pass around to complete the event. In some events, the pylons can be as far as forty or more feet laterally from the boat. The motion of the water-skier quickly goes from one side of the boat to the other as the skier attempts to successfully negotiate and pass each pylon. The speed of the skier is quite fast as he/she moves from one pylon across to the next in a matter of seconds. As a result of this speed, the pulling force acting on the stern of the boat rapidly changes both magnitude and direction as the skier passes from one side of the boat to the other.
During the slalom event, the powerboat must steer a straight course through a channel defined by another set of pylons while the skier is in tow. Due to the speed of the water-skier passing from one side of the boat to the other, the dynamic force generated by the skier can cause a tremendous pulling on the stern which can cause the boat to veer from its straight line course through the pylons. Therefore, the driver must constantly compensate for the pulling forces on the stern since the slalom is a high speed and high performance event of limited duration. The operator generally does this by trying to simultaneously watch the motion of the skier while looking forward to stay within the pylons.
Therefore, there is a need for a steering system which allows a powerboat to successfully tow a water-skier and compensates for the dynamic effect of the towed skier on the boat. Such a system should compensate for the directional control problems caused by the pulling force on the boat both when a straight line course is being followed or when the boat enters into a turn. Additionally, such a steering system would also be beneficial if it allows powerboats to negotiate tighter, high speed turns without loss of speed.